In order to downsize a transmission and increase output torque, for example, a transmission apparatus disclosed in JP2002-70960A, adapted to a front-engine front-drive type vehicle to which an engine connected in an axial direction thereof are transversely mounted, includes an input shaft, two counter shafts and plural shift stage gear sets that are arranged in parallel to each other between the input shaft and each of the counter shafts, thereby shortening length of the transmission apparatus in an axial direction thereof without reducing number of shift stages. A transmission 1 illustrated in FIG. 4 has substantially the same structure as the transmission apparatus disclosed in the second embodiment of JP2002-70960A. As illustrated in FIG. 4, an input shaft 3a, first counter shaft 3b, a second counter shaft 3c and a reverse shaft 3d are arranged in parallel to each other within a transmission case 2. The first counter shaft 3b and the second counter shaft 3c are connected to output shafts 8a and 8b via reduction gear set 6a, 6b and 6c and a differential mechanism 7. A first forward movement gear switching unit 4A forming a 1st shift stage and a 2nd shift stage and a second forward movement gear switching unit 4B forming a 3rd shift stage and a 4th shift stage are arranged between the input shaft 3a and the first counter shaft 3b so that the second forward movement gear switching unit 4B is positioned farther away from an engine 10 than the first forward movement switching unit 4A. A third forward movement switching unit 4C forming a 5th shift stage and a 6th shift stage is arranged between the input shaft 3a and the second counter shaft 3c so as to be located at a position substantially corresponding to the position where the second forward movement gear switching unit 4a is arranged, in an axial direction of the input shaft 3a. Further, a reverse movement gear switching mechanism 4D forming a reverse shift stage is arranged between the input shaft 3a, the second counter shaft 3c and the reverse shaft 3d so as to be located at a position substantially corresponding to the position where the first forward movement gear switching unit 4A is provided, in the axial direction of the input shaft 3a. A back wall portion 2a of the transmission case 2, substantially corresponding to an area where input shaft 3a, the first counter shaft 3b and the second counter shaft 3c are arranged orthogonally relative to the back wall portion 2a, is formed to have a flat surface.
FIG. 5 schematically illustrates a forward portion of the vehicle, viewed in a lateral direction thereof, to which a driving unit is transversely mounted at the forward portion of a vehicle body. The driving unit is a unit in which the transmission 1 disclosed in JP2002-70960A is connected to the engine 10 in an axial direction thereof. As illustrated in FIG. 5, the driving unit is positioned between a pair of side frames 9 extending along both sides of the vehicle body in a front-rear direction thereof. In order to prevent the side frames 9 from interfering with a front axle, forward portions of the side frames 9 are curved upwardly. Hence, as illustrated in FIG. 6, the side frame 9 at the left side in FIG. 5 extends along immediate left of an upper portion of the back wall portion 2a of the transmission case 2 in the front-rear direction of the vehicle.
In order to increase collision safety and vehicle stiffness, a cross-section of each of the side frames 9 needs to be enlarged and a shape of each of the side frames 9 needs to be linearized. The side frames 9a having the enlarged cross-sectional area and the linearized shape are illustrated with chain double-dashed lines in FIG. 5. As is evident from the position of the side frames 9a having the enlarged cross-section and illustrated with the chain double-dashed lines in FIG. 5, the side frame 9a at the left side in FIG. 5 interferes with an upper left portion of the back wall portion 2a of the transmission case 2, and the side frame 9a at the right side in FIG. 5 is positioned closer to the engine 10. Hence, the driving unit having axially connected engine 10 and transmission 1 may have difficulties when being transversely mounted on the vehicle body. A case where the driving unit, in which the engine and the transmission are connected in the axial direction thereof, is adapted to the front-engine front-drive type vehicle is described above. However, as is the case with the transmission adapted to the front-engine front-drive type vehicle described above, in a case where a similar driving unit is adapted to a rear-engine rear-drive type vehicle, the driving unit in which the transmission 1 and the engine 10 connected in the axial direction thereof may have difficulties when being transversely mounted on the vehicle body because of the similar reasons explained above.
The transmission apparatus disclosed in JP2002-70960A suggests a modified transmission apparatus in which a portion of the back wall of the transmission case positionally corresponding to the second counter shaft is arranged closer to the engine, compared to a portion of the back wall positionally corresponding to the first counter shaft, by eliminating one shift stage. However, in the transmission apparatus disclosed in JP2002-70960A, the portion on the back wall, corresponding to the second counter shaft and positioned closer to the engine than other portions of the back wall, is positioned at lower portion of the transmission case, thus resulting in creating a dead space at the back wall portion of the transmission case. Hence, even with the modified transmission apparatus disclosed in JP2002-70960A, the driving unit may have difficulties when being transversely mounted on the vehicle.
A need thus exists for a vehicle which is not susceptible to the drawback mentioned above.